What are fossils? Describe briefly two methods of determining the age of fossils.

Explanation

### Step-by-Step Solution

**Step 1: Definition of Fossils**
Fossils are the preserved remains or traces of organisms that lived in the past. They are typically the remains of dead organisms that have become extinct and are no longer present on Earth. Fossils are formed when these remains are buried under sediment and are unable to decay, leading to their preservation over time.

**Step 2: Method 1 - Radiometric Dating**
One method of determining the age of fossils is radiometric dating. This technique involves measuring the concentration of radioactive elements within the fossil or the surrounding rocks. By analyzing the decay of these radioactive isotopes, scientists can estimate the age of the fossil. The most commonly used isotopes for dating are Carbon-14, Uranium-238, and Potassium-40.

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